This invention relates, in general, to interconnect technology, and more particularly to the interconnection of a semiconductor chip to a substrate.
Integrated circuits or semiconductor chips are being designed to form systems of increased complexity and performance. Advances in semiconductor chip technology have drastically increased the functionality and speeds of a semiconductor chip; these advances are mainly due to smaller device sizes and multiple layers of interconnect. Likewise, the increased functionality and speed of an individual semiconductor chip has increased the number of off chip connections which must be made when coupling multiple integrated circuits to form a system. Performance is not only linked to individual integrated circuit speeds but also interconnect delay between semiconductor chips. The pursuit of high density/high performance chip to chip interconnect has brought about many new concepts to this technology.
A popular solution to minimize performance impacts of inter-chip connections is to mount semiconductor chips on a common substrate. The common substrate has one or more layers of interconnect to couple the semiconductor chips together. The semiconductor chips are mounted as close as possible on the common substrate to minimize interconnect distance between chips. Assuming a common substrate approach is utilized to interconnect multiple semiconductor chips it is still imperative to develop a reliable means of coupling each external connection terminal of each semiconductor chip to a corresponding connection terminal on a common substrate.
Many types of interconnect have been developed for coupling semiconductor chip external connection terminals to a substrate. Among the most popular connection schemes are bumping processes. A raised conductive bump is placed on each external connection terminal of a semiconductor chip and/or a corresponding group of terminals on a substrate. Aligning and placing a semiconductor chip on a substrate allows each conductive bump to connect an external connection terminal of a semiconductor chip to a corresponding terminal on the substrate. Conductive bumps form not only an electrical connection but also a physical connection which holds a semiconductor chip to a substrate. Conductive bumps can be formed from many types of materials ranging from solder to conductive polymers. Each type of material used to form a conductive bump will have it's own process flow and production requirements.
General problems with bumping include process temperatures (for some types of bumping), difficulty of rework, testing, the ability to bump semiconductor chips from outside vendors, and cost. Bumping is a solution that many manufacturers have pursued despite these difficulties because it allows the formation of a high performance multiple chip system in a small area.
It would be of great benefit if an external interconnect system could be developed that couples a semiconductor chip's external connection terminals to a corresponding group of terminals on a substrate which is low cost, uses existing process technology and equipment, has a small number of process steps, can provide permanent or temporary connection, and is easily formed on a majority of semiconductor chips currently sold on the open market. Such an interconnect system would be of great benefit in post-manufacturing testing and burn-in testing.